Unloader Blowout Issue?

[AdvWindowCleaning 14]

Hello all, a question for you from a maintenance and repairs newbie. I had my machine go out today due to what I assume is an unloader issue. While running the machine there was a sudden pressure drop, and then repetitive surges of slight pressure build up followed by pressure drops. Upon examining the machine, blasts of water spray were seen coming out of the unloader (at the location marked by the red arrow below) with each pressure drop at the wand end. Can anyone tell me what has happened here and what I need to do to repair it? Machine: 5.0gpm 3000psi hot water. Thanks, Jason

[Douglas Hicks 128]

I am not Jason,but I think I can help. That is a thermal relief valve. It blew because it got too hot. Buy another one, install it and go back to work. You have taxes to pay.

[Russ Johnson 141]

That is a high pressure relief valve. If the unloader is set too high or fails to unload, that valve pops off before something else more costly does. It may have just gone bad, too.

[big mike 14]

That is a high pressure relief valve

Pressure relief yes, thermal relief no. Also sometimes called a "burst disc" valve. Once they go bad, they have to be replaced. They run around ten bucks, and you should keep a couple on hand. They are adjustable, but are set to 6000 psi from the factory (usually). When this blows, it signals an issue elsewhere in the system causing a high pressure spike. Probably an unloader issue.

After looking at your setup, I think the relief valve is placed incorrectly on the system? All of my rigs have the relief valve AFTER the unloader.....

Edited May 11, 2010 by big mike
additional info

[Scott Stone 604]

That is a strange place for a relief valve to be located.

[Ron Musgraves 240]

STop hooking up to hotwater...

[AdvWindowCleaning 14]

Pressure relief yes, thermal relief no. Also sometimes called a "burst disc" valve. Once they go bad, they have to be replaced. They run around ten bucks, and you should keep a couple on hand. They are adjustable, but are set to 6000 psi from the factory (usually). When this blows, it signals an issue elsewhere in the system causing a high pressure spike. Probably an unloader issue.

After looking at your setup, I think the relief valve is placed incorrectly on the system? All of my rigs have the relief valve AFTER the unloader.....

Thanks for the responses guys. The machine is about 6 or 7 years old, purchased from Delco of Fort Worth. Never had this issue before and I have not made any adjustments or modifications to the assembly as shown in the picture. So it doesn't make sense in its current location? Mike, you noted that when the relief goes bad it a sign of things wrong else where - is there something I should do to the unloader? Do I need to replace it as well? Ron, "Stop hooking up to hot water"?

[Russ Johnson 141]

That is a strange place for a relief valve to be located.

No different than if it were on the head of the pump...

[AdvWindowCleaning 14]

No different than if it were on the head of the pump...

Meaning it is okay to be there or not?

[Russ Johnson 141]

Yes, it's fine.

[AdvWindowCleaning 14]

Thanks Russ.

So the high pressure relief valve is a back-up to the unloader correct? I have to order the relief valve and have it shipped, as I do not have a supplier local. Could I get by for one small patio job tomorrow if I was to remove the current high pressure relief valve from the assembly and run the machine without it?

[tonyshelton 112]

It will also pop if you let your stuff freeze. Don't ask how I know.

[Scott Stone 604]

The machine will run fine without it. Be warned that they are a safety device, and are totally unnecessary, well, until there is a problem.

As for the location, I am used to them being on the other side of the unloader, not between the pump and the unloader. If I remember right, that is where the Delco machines I have bought have always had them.

[offduty 25]

I have never had one on any of my machines. One more thing to leak or go bad.